Assumption reinsurance is a form of reinsurance

Reinsurance

Reinsurance is insurance that is purchased by an insurance company from another insurance company as a means of risk management...

 whereby the reinsurer is substituted for the ceding insurer and becomes directly
liable

Legal liability

Legal liability is the legal bound obligation to pay debts.* In law a person is said to be legally liable when they are financially and legally responsible for something. Legal liability concerns both civil law and criminal law. See Strict liability. Under English law, with the passing of the Theft...

for policy claims. This ordinarily requires a notice and release from affected policyholders. In the more typical reinsurance arrangement, the reinsurer has an obligation to indemnify the ceding insurer, which remains liable for claims on policies it has issued, and policyholders' approval is not required.